In vitro assessment of silver-containing gelling fiber dressings against wound surface-associated antibiotic-resistant pathogens

Introduction: In vitro assessment of silver-containing gelling fiber dressings against wound surface-associated antibiotic-resistant pathogensMethods:Four silver-containing dressings were evaluated: carboxymethylcellulose (CMC) dressing containing ionic silver, ethylenediaminetetraacetic acid (EDTA) and benzethonium chloride (BEC; ‘CISEB’*); CMC dressing containing silver oxysalts†; polyacrylate (polyabsorbent) fiber dressing with an acrylic core and silver sulphate‡; and non-woven polyvinyl alcohol fiber dressing containing silver sulphate§. In brief, challenge microorganisms (antibiotic-resistant Pseudomonas aeruginosa [RPA] and community-associated methicillin-resistant Staphylococcus aureus [CA-MRSA]) were grown on gauze to simulate the surface-associated phenotype and transferred to a simulated wound assembly (SWA). Test dressings were applied and covered with a transparent film dressing, and the SWA was then incubated at 35±3 ºC for up to 120 hours. Enumeration of surviving bacteria was performed in triplicate for each test dressing.Results:All test dressings reduced levels of surface-associated microorganisms within 6 hours. CISEB demonstrated the greatest reduction, reducing the RPA population by ~6 log10 (million-fold reduction) by 48 hours. The kill rate with CISEB was sustained for the duration of the challenge period, reducing the RPA population to non-detectable levels (8.8 log10 reduction). Similar antimicrobial activity was observed against CA-MRSA, with CISEB reducing the CA-MRSA population by >5 log10 by 48 hours and to non-detectable levels by 96 hours, which was maintained until the end of the test period (120 hours). Cell survival for both species remained comparatively high throughout the test period for the other test dressings.Discussion: CISEB demonstrated superior antimicrobial activity against surface-associated microorganisms compared with other silver-containing gelling fiber dressings. Despite all test dressings containing silver, CISEB demonstrated enhanced antimicrobial activity, which may be attributed to the additional agents (EDTA and BEC) that act synergistically to disrupt the EPS matrices.  References: